Scroll fluid machine

ABSTRACT

A gap between opposing wrap portions is narrowed to increase compression efficiency, and an amount of machining time is reduced to thereby increase productivity. 
     A plurality of proximate portions  8  are formed, at spacings in a spiral direction, on an outer peripheral surface  3 B of a wrap portion  3  of a fixed scroll  1 . Flat surfaces  8 A are used to connect adjacent proximate portions  8 . Similarly, a plurality of proximate portions  14  are formed, at spacings in the spiral direction, on an outer peripheral surface  13 B of a wrap portion  13  of an orbiting scroll  11.  Flat surfaces  14 A are used to connect adjacent proximate portions  14 . In this way, the outer peripheral surfaces  3 B and  13 B of the wrap portions  3  and  13  can be formed in polyangular shapes, so as to reduce a gap between the wrap portions  3  and  13  and simplify the shapes. As a result, an amount of machining time can be reduced.

BACKGROUND OF THE INVENTION

The present invention relates to a scroll fluid machine suitable for use as an air compressor, a vacuum pump, etc. by way of example.

In general, a scroll fluid machine includes a fixed scroll and an orbiting scroll provided facing the fixed scroll. The fixed scroll and the orbiting scroll each have a disk-shaped end plate and a wrap portion projecting axially from the end plate. The wrap portion is wound spirally from the radially inner side toward the radially outer side of the end plate. Thus, the fixed scroll and the orbiting scroll define a plurality of compression chambers by overlapping of their wrap portions.

In the scroll fluid machine, the orbiting scroll is driven by a driveshaft to perform an orbiting motion with respect to the fixed scroll with a predetermined orbiting radius, thereby sucking a fluid, e.g. a gas, from a suction opening provided in a radially outer part of the fixed scroll, and successively compressing the fluid in the compression chambers. Finally, the compressed fluid is discharged to the outside from a discharge opening provided in a radially inner part of the fixed scroll.

There is known a scroll fluid machine having a plurality of projections on peripheral surfaces of wrap portions to reduce a gap between the wrap portions, and thereby increase a degree of hermeticity of compression chambers, and improve a compression efficiency [for example, refer to Japanese Patent Application Unexamined Publication (KOKAI) No. 2004-138056 and Japanese Patent Application Unexamined Publication (KOKAI) No. 2004-293487]. The plurality of projections are spaced apart in a direction of winding (spiral direction), on the peripheral surfaces of the wrap portions, so as to project relative to their surrounding in a radial direction from the peripheral surfaces of the wrap portions.

SUMMARY OF THE INVENTION

It is to be noted that the above-described conventional scroll fluid machine has a plurality of axially extending projections on the peripheral surfaces of the wrap portions to minimize an amount of compressed fluid leaking through mutually opposing wrap portions, so as to increase a degree of hermeticity in the compression chambers.

In the prior art, however, portions recessed in a radial direction are formed between adjacent projections. Although the projections make contact with the wrap portion of the mating scroll, the recessed portions do not make contact with the wrap portion of the mating scroll. Therefore, air filled in the recessed portions is not compressed but rather leaks into a lower pressure side after the peripheral surface of the mating wrap portion has passed. As a result, a compression efficiency remains low.

Further, to form the projections on the peripheral surfaces of the wrapped portions that are curved, a working tool such as an end mill needs to be moved back and forth in the radial direction along the projections, which is likely to give rise to machining errors. Further, the complicated machining process gives rise to problems such as a prolonged machining time and low productivity.

The present invention has been made in view of the above-described problems in the prior art. An object of the present invention is to provide a scroll fluid machine that has a narrowed gap between mutually opposing wrap portions to improve compression efficiency and that helps reduce an amount of machining time to thereby enhance productivity.

The present invention provides a scroll fluid machine comprising: a first scroll having a wrap portion projecting axially from an end plate, said wrap portion being wound spirally from a radially inner side toward a radially outer side of said end plate; and a second scroll provided facing said first scroll, said second scroll having a wrap portion projecting axially from an end plate, said wrap portion being wound spirally from a radially inner side toward a radially outer side of said end plate so as to overlap the wrap portion of said first scroll to define a plurality of compression chambers.

To solve the above described problems, according to the invention, a plurality of proximate portions are formed at least on an outer peripheral surface of the wrap portion of the first scroll, the plurality of proximate portions being adapted to make contact with or come closest to an inner peripheral surface of the wrap portion of the second scroll and being spaced apart in a winding direction; the adjacent proximate portions are connected by flat surfaces or convex surfaces; and the flat surfaces or convex surfaces are positioned farther than the proximate portions away from the second scroll.

A plurality of flat, concave, or convex proximate surfaces may be formed on an inner peripheral surface of the wrap portion of the second scroll, the plurality of flat, concave, or convex proximate surfaces being adapted to make contact with or come closest to the proximate portions formed on the outer peripheral surface of the wrap portion of the first scroll and being spaced apart in the winding direction.

A film-like soft coating, which is made of a material softer than that of the proximate portions, may be applied to at least either the outer peripheral surface of the wrap portion of the first scroll or the inner peripheral surface of the wrap portion of the second scroll.

The proximate portions may be formed such that a pitch thereof in the winding direction is narrow on the radially inner side and wide on the radially outer side.

The proximate portions may be formed at equal angular spacings throughout the wrap portion from the radially inner side to the radially outer side.

The proximate portions may be formed only on a part of the wrap portion away from the end plate in the axial direction, the wrap portion projecting from the end plate.

The proximate portions may be formed only on the radially inner side of the wrap portion in the winding direction, and an involute curved surface is formed along an involute curve on the radially outer side of the wrap portion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional view showing a scroll air compressor according to a first embodiment of the present invention.

FIG. 2 is a transverse sectional view of the scroll air compressor as seen from the direction of the arrow II-II in FIG. 1.

FIG. 3 is an enlarged fragmentary transverse sectional view showing a wrap portion of a fixed scroll and a wrap portion of an orbiting scroll in FIG. 2.

FIG. 4 is a partially-cutaway enlarged perspective view of an end plate, a wrap portion, and proximate portions of a fixed scroll.

FIG. 5 is an enlarged transverse cross-sectional view of the essential part of the proximate portion of the wrap portion of the orbiting scroll.

FIG. 6 is a transverse cross-sectional view of the wrap portion while being machined using an end mill.

FIG. 7 is a transverse cross-sectional view of a wrap portion according to a first modified example.

FIG. 8 is a transverse cross-sectional view of a scroll air compressor according to a second embodiment.

FIG. 9 is an enlarged transverse cross-sectional view of the essential portions of the wrap portions of the fixed scroll and orbiting scroll shown in FIG. 8, as viewed from the same perspective as FIG. 3.

FIG. 10 is a transverse cross-sectional view of the wrap portion according to a second modified example.

FIG. 11 is an enlarged-transverse cross-sectional view of the essential portions of wrap portions of a fixed scroll and an orbiting scroll according to a third embodiment, as viewed from the same perspective as FIG. 3.

FIG. 12 is an enlarged transverse cross-sectional view of the essential portions of wrap portions of a fixed scroll and an orbiting scroll according to a fourth embodiment, as viewed from the same perspective as FIG. 3.

FIG. 13 is a partially-cutaway enlarged perspective view of an end plate, a wrap portion and proximate portions of the fixed scroll shown in FIG. 12.

FIG. 14 is an enlarged longitudinal cross-sectional view of the essential portions of the wrap portions of the fixed scroll and orbiting scroll, as viewed in the direction of an arrow XIV-XIV of FIG. 12.

FIG. 15 is a transverse cross-sectional view of a scroll air compressor according to a fifth embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Below, scroll fluid machines according to embodiments of the present invention are described in detail by way of examples of scroll air compressors with reference to accompanying figures.

FIGS. 1 to 6 show the first embodiment, which is described below, giving an example in which proximate portions are formed on outer peripheral surfaces of wrap portions of a fixed scroll and orbiting scroll.

FIG. 1 is a longitudinal cross-sectional view of the scroll air compressor. In FIG. 1, reference numeral 1 denotes the fixed scroll of the scroll air compressor. The fixed scroll 1 is attached to an end of a cylindrical casing (not shown). The fixed scroll 1 mainly comprises: an end plate 2 of a substantially disk shape disposed such that the center of the end plate 2 corresponds to an axis O1-O1 of a driveshaft 9 (described later); a spiral wrap portion 3 formed on a surface 2A of the end plate 2; a cylindrical portion 4 projecting axially from the outer peripheral edge of the end plate 2 so as to surround the wrap portion 3; and a flange portion 5 extending radially outward from the cylindrical portion 4.

FIG. 2 is a transverse sectional view of the scroll air compressor shown in FIG. 1. As shown in FIG. 2, the wrap portion 3 is formed in a spiral shape in which the radially inner end (an inner side in a radial direction) of the wrap portion 3 is a spiral starting end, and the radially outer end (an outer side in the radial direction) of the wrap portion 3 is a spiral terminating end. The inner peripheral surface 3A of the wrap portion 3 has a smooth concave shape without projections or recesses. On the other hand, the outer peripheral surface 3B of the wrap portion 3 is formed in a polyangular shape in which a plurality of flat surfaces 8A (described later) are connected together. As shown in FIG. 6, the wrap portion 3 is formed in a spiral shape, using a cutting tool such as an end mill.

As shown in FIG. 1, the fixed scroll 1 has a suction opening 6 provided in an outer peripheral portion of the end plate 2 to suck air into compression chambers 15 (described later) therethrough. The center of the end plate 2 is provided with a discharge opening 7 for discharging air compressed in the compression chambers 15.

Reference numeral 8 denotes a plurality of proximate portions formed on the outer peripheral surface 3B of the wrap portion 3. As shown in FIGS. 2 and 3, the proximate portions 8 are disposed at spacings in the winding direction (direction of length) of the wrap portion 3 and extend in the axial direction. An angle α between adjacent proximate portions 8 is set to, for example, about 5 degrees (α=0.087 (rad)).

Flat surfaces 8A are used to connect adjacent proximate portions 8. Therefore, the outer peripheral surface 3B of the wrap portion 3 has a polyangular shape in transverse cross section, such that the proximate portions 8 are located at apexes (bent portions) of the polyangular outer peripheral surface 3B. The proximate portions 8 make contact with or come closest to an inner peripheral surface 13A of the wrap portion 13 of the mating orbiting scroll 11.

A position in which the wrap portion 3 of the fixed scroll 1 and the wrap portion 13 of the orbiting scroll 11 come closest to each other varies according to an orbiting motion of the orbiting scroll 11, and gradually moves from the spiral terminating ends (on the radially outer side) to the spiral starting ends (on the radially inner side) of the wrap portions 3 and 13. Therefore, the flat surfaces 8A can come closer than the proximate portions 8 to the wrap portion 13 of the orbiting scroll 11. However, the proximate portions 8 refer to apexes of the polyangular outer peripheral surface 3B. Therefore, the distance by which the proximate portions 8 and the wrap portion 13 come closest to each other is shorter than that by which the flat surfaces 8A and the wrap portion 13 come closest to each other. In other words, the flat surfaces 8A are more spaced apart than the proximate portions 8 from the inner surface 13A of the wrap portion 13 of the orbiting scroll 11.

A driveshaft 9 is rotatably provided in the casing. The driveshaft 9 has an axis O1-O1 as the center of rotation. An end portion of the driveshaft 9 closer to the fixed scroll 1 extends eccentrically to form a crankshaft 9A. The center axis O2-O2 of the crankshaft 9A is eccentric with respect to the axis O1-O1 of the driveshaft 9 by an orbiting radius ε. The crankshaft 9A of the driveshaft 9 rotatably supports an orbiting scroll 11 (described later) through an orbiting bearing 10.

The orbiting scroll 11 is provided on the driveshaft 9 to face the fixed scroll 1. The orbiting scroll 11 mainly comprises: an end plate 12 formed to have the shape of a disk centered at the axis O2-O2; and a spiral wrap portion 13 projecting axially from a surface 12A of the end plate 12.

The orbiting scroll 11 is positioned so that the wrap portion 13 overlaps the wrap portion 3 of the fixed scroll 1 with an offset angle of 180 degrees, for example. Thus, a plurality of compression chambers 15 (described later) are defined between the two wrap portions 3 and 13. During the operation of the scroll air compressor, air is sucked into the radially outermost compression chamber 15 from the suction opening 6, and the sucked air is successively compressed in the compression chambers 15 while moving toward the radially inner side during the orbiting motion of the orbiting scroll 11. Finally, the compressed air is discharged to the outside from the discharge opening 7.

The wrap portion 13 of the orbiting scroll 11 projects axially (direction of the axis O1-O1) from the surface 12A of the end plate 12. The wrap portion 13 is formed in a spiral shape with n turns in which the radially inner end of the wrap portion 13 is a spiral starting end, and the radially outer end of the wrap portion 13 is a spiral terminating end. Further, the inner peripheral surface 13A of the wrap portion 13 is formed to have a smooth concave shape without recesses or projections. On the other hand, the outer peripheral surface 13B of the wrap portion 13 is formed in a polyangular shape in which a plurality of flat surfaces 14A (described later) are connected together. As shown in FIG. 6, the wrap portion 13 is spirally formed, using a cutting tool such as an end mill.

Reference numeral 14 denotes a plurality of proximate portions formed on the outer peripheral surface 13B of the wrap portion 13. As shown in FIGS. 2 and 3, the proximate portions 14 are spaced apart in the winding direction (direction of length) of the wrap portion 13 in a manner similar to the proximate portions 8 and extend in the axial direction. The angle α between adjacent proximate portions 14 is set to, for example, about 5 degrees (α=0.087 (rad)).

Flat surfaces 14A are used to connect the adjacent proximate portions 14. Therefore, the outer peripheral surface 13B of the wrap portion 13 is formed to have a polyangular shape in transverse cross section, such that the proximate portions 14 are located at apexes (bent portions) of the polyangular outer peripheral surface 13B. The proximate portions 14 are adapted to make contact with or come closest to an inner peripheral surface 3A of the wrap portion 3 of the mating orbiting scroll 1.

A position in which the wrap portion 3 of the fixed scroll 1 and the wrap portion 13 of the orbiting scroll 11 come closest to each other varies according to an orbiting motion of the orbiting scroll 11. Therefore, the flat surfaces 14A can come closer than the proximate portions 14 to the wrap portion 3 of the fixed scroll 1. However, the proximate portions 14 refer to apexes of the polyangular outer peripheral surface 13B. Therefore, the distance by which the proximate portions 14 and the wrap portion 3 come closest to each other is shorter than that by which between the flat surfaces 14A and the wrap portion 3 come closest to each other. In other words, the flat surfaces 14A are spaced further apart than the proximate portions 14 from the inner peripheral surface 3A of the wrap portion 3 of the fixed scroll 1.

Next, a positional relationship of the proximate portions 14 formed on the outer peripheral surface 13B of the wrap portion 13 of the orbiting scroll 11 is described in detail.

The proximate portions 14 are formed such that a pitch P in the winding direction, which is a direction of length of the wrap portion 13, is narrow on the radially inner side and wide on the radially outer side. Detailed description will now be given of the arrangement of the proximate portions 14. For the orbiting scroll 11, as shown in FIG. 3, an evolute C with an evolute radius a centered at the center O2 (position of the axis O2-O2) of the orbiting scroll 10 is obtained to trace an involute of the wrap portion 13. It should be noted that the evolute radius a is a value characteristic of the orbiting scroll 11 determined by the orbiting radius ε and the thickness of the wrap portion 13 of the orbiting scroll 11, which is a known term in association with involute curves.

Assuming that, of innumerable tangents to the evolute C, an arbitrary tangent is L1 and other tangents offset successively from the tangent L1 by an angle α are L2, L3 and so forth, the proximate portions 14 are positioned on the tangents L1, L2 and so forth, respectively.

In this embodiment, the angle α between each pair of adjacent tangents L1, L2 and so forth is set at about 5 degrees. Thus, the pitch P between adjacent proximate portions 14 in the winding direction is narrow in the 1st turn of the wrap portion 13 at the radially inner end thereof and is wide in the nth turn of the wrap portion 13 at the radially outer end thereof.

By setting the pitch P between adjacent proximate portions 14 narrow (small) at the radially inner side as stated above, the proximate portions 14 can be placed with a predetermined gap with respect to the opposing inner peripheral surface 3A of the wrap portion 3 even at a part where the radius of curvature of the wrap portion 3 is small and hence the curvature of the wrap portion 3 is steep.

Further, the gap S2 defined between the proximate portions 14 and the opposing inner peripheral surface 3A of the wrap portion 3 of the fixed scroll 1 when the proximate portions 14 approach the inner peripheral surface 3A is set to be larger than the gap S1 defined between the proximate portions 8 and the opposing inner peripheral surface 13A of the wrap portion 13 of the orbiting scroll 11 when the proximate portions 8 approach the inner peripheral surface 13A as given by the following equation 1:

S1<S2   [Eq. 1]

As described above, the gap S2 between the proximate portions 14 and the wrap portion 3 is larger than the gap S1 between the proximate portions 8 and the wrap portion 13. In this way, when the wrap portions 3 and 13 are brought into contact with each other, the proximate portions 8 of the outer peripheral surface 3B of the wrap portion 3 of the fixed scroll 1 can be brought into contact with the outer peripheral surface 13B of the wrap portion 13 of the orbiting scroll 11 before the proximate portions 14 and the outer peripheral surface 3B of the wrap portion 3 make contact.

When the proximate portions 8 of the wrap portion 3 of the fixed scroll 1 first make contact with the wrap portion 13 of the orbiting scroll 11, a force acts on the orbiting scroll 11 in such a manner that the contact portions serve as fulcrums, causing the orbiting scroll 11 to rotate in the same direction as that of a rotating force. Thus, the orbiting scroll 11 is pressed in the direction of the rotating force. Accordingly, it is possible to eliminate backlash in a rotation-preventing mechanism (not shown) provided between the orbiting scroll 11 and the casing, for example.

The proximate portions 8 provided on the outer peripheral surface 3B of the wrap portion 3 of the orbiting scroll 1 are formed under conditions similar to those concerning the positional relationship and so forth of the proximate portions 14 described above. Therefore, description thereof is omitted.

It is to be noted that, instead of forming the proximate portions 8 and 14 along the entire spiral lengths of the wrap portions 3 and 13, the proximate portions 8 and 14 can be formed, for example, on regions of the outer peripheral surfaces 3B and 13B except for regions ranging about half a turn from the spiral starting ends that are the radially innermost sides. The regions of the outer peripheral surfaces 3B and 13B of the wrap portions 3 and 13 ranging about half a turn from the spiral starting ends have the smallest radius of curvature and are less likely to change in size under the influence of heat; therefore, these regions are formed into smooth surfaces since the compression chamber 15 can be closed tightly enough without provision of proximate portions 8 and 14 at these regions.

The structure of the scroll air compressor according to this embodiment is as described above. Next, operation of the scroll air compressor is described.

First, when the driveshaft 9 is driven to rotate by a drive source (not shown), e.g. an electric motor, the orbiting scroll 11 performs an orbiting motion with an orbiting radius ε about the axis O1-O1 of the driveshaft 9 in such a state as to be prevented from rotating around its own axis by the rotation-preventing mechanism. The compression chambers 15, which are defined between the wrap portion 3 of the fixed scroll 1 and the wrap portion 13 of the orbiting scroll 11, are successively contracted by the orbiting motion of the orbiting scroll 11. Thus, the air sucked in from the suction opening 6 of the fixed scroll 1 is successively compressed in the compression chambers 15, and the compressed air is discharged from the discharge opening 7 of the fixed scroll 1 to an external tank (not shown).

When the orbiting scroll 11 makes an orbiting motion relative to the fixed scroll 1, the proximate portions 8 and 14 and the inner peripheral surfaces 13A and 3A of the wrap portions 13 and 3 come closest to or make contact with each other. These proximate (contact) portions correspond to trapping positions for trapping air in the compression chambers 15. The proximate portions 8 when being positioned at the trapping positions of the compression chambers 15 reduce a gap between the outer peripheral surface 3B of the wrap portion 3 and the inner peripheral surface 13A of the wrap portion 13. The proximate portions 14 when being positioned at the trapping positions of the compression chambers 15 reduce a gap between the outer peripheral surface 13B of the wrap portion 13 and the inner peripheral surface 3A of the wrap portion 3. In this way, the proximate portions 8 and 14 can enhance the degree of hermeticity of the compression chambers 15.

In this embodiment, a plurality of proximate portions 8 and 14 are formed, at spacings in the winding direction, on the outer peripheral surfaces 3B and 13B of the wrap portions 3 and 13 of the scroll 1 and 11, such that adjacent proximate portions 8 and 14 are connected by flat surfaces 8A and 14A to form the outer peripheral surfaces 3B and 13B in a polyangular shape. Since the flat surfaces 8A and 14A are used to connect the adjacent proximate portions 8 and 14, there is no portion recessed in the radial direction between adjacent projections, as in the prior art. Therefore, the gap between the opposing wrap portions 3 and 13 can be narrowed to reduce an amount of air filled between the wrap portions 3 and 13 and thus to enhance the compression efficiency.

Since the flat surfaces 8A and 14A are used to connect the adjacent proximate portions 8 and 14, the outer peripheral surfaces 3B and 13B of the wrap portions 3 and 13 can be formed in a polyangular shape in transverse cross section. Therefore, compared to a conventional case in which projections are formed on a curved peripheral surface of a wrap portion, the shapes of the wrap portions 3 and 13 can be simplified. As a result, when the wrap portions 3 and 13 are formed using a cutting tool such as an end mill, the end mill does not have to be moved back and forth in a radial direction along the projections, and a number of times that the direction of movement of the tool needs to be changed can be reduced. In general, processing machines cause machining errors of about 5 μm due to backlash during reciprocating movements. This embodiment is less susceptible to the influence of such backlash. Therefore, any machining error can be reduced, and wrap portions 3 and 13 can be produced at a consistently high precision.

Compared to a conventional case in which projections are formed, the distance of movement of a tool such as an end mill can be reduced, and the number of times the direction of movement of the tool needs to be changed can be reduced. Therefore, the amount of time required to produce wrap portions 3 and 13 can be reduced with a result of increased productivity. A machining program can be readily made simply by providing coordinates of apexes of the polyangular shape, and the coordinates of the apexes can be readily changed. Therefore, the shapes of the wrap portions 3 and 13 can be readily changed according to, for example, specifications of a compressor.

Further, the proximate portions 8 of the wrap portion 3 make surface contact, close to line contact, with the inner peripheral surface 13A of the mating wrap portion 13. Such contact can readily blunt or wear down the proximate portions 8. Therefore, the proximate portions 8 of the wrap portion 3 can be fitted with the inner peripheral surface 13A of the wrap portion 13, before making contact with it a large number of times. Similarly, the proximate portions 14 of the wrap portion 13 can readily fit with the inner peripheral surface 3A of the mating wrap portion 3. This makes it possible to reduce power loss and to prevent damage, noise, galling, and so on and to enhance durability and reliability.

Further, as the angle α between adjacent proximate portions 8 and 14 of the wrap portion 3 and 13 increases, the interior angle (an angle made by two adjacent flat surfaces 8A, 14A) of the proximate portion 8, 14 becomes acute; thus, galling resistance can be improved. However, the gap between the flat surface 8A and the outer peripheral surface 13A and the gap between the flat surface 14A and the outer peripheral surface 3A increases; thus, a compression performance is impaired. On the other hand, as the angle α between two adjacent proximate portions 8 and 14 of the wrap portion 3 and 13 decreases, the interior angle of the proximate portion 8, 14 becomes obtuse; thus, a galling resistance is reduced. However, the gap between the flat surface 8A and outer peripheral surface 13A and the gap between the flat surface 14A and the outer peripheral surface 3A decrease; thus, a compression performance can also be improved. Therefore, by setting the angle α to, for example, about 5 degrees (α=0.087 (rad)), a balance between these opposing properties can be optimized to produce a compressor having a well-balanced galling resistance and compression performance.

On the other hand, by setting the angle α to about 5 degrees, the pitch P of adjacent proximate portions 8 and 14 in the winding direction of the wrap portion 3 and 13 is narrow on the radially inner side and wide on the radially outer side. Therefore, even for a sharply curved part of the wrap portions 3, 13 having a small radius of curvature, the proximate portions 8, 14 having a narrow pitch P in the winding direction can be closely fit along the inner peripheral surface 13A and 3A of the mating wrap portion 13 and 3. As a result, a degree of hermeticity of the compression chamber 15 can be improved, and compression performance can be enhanced.

Further, the space S1 between the proximate portion 8 of the wrap portion 3 of the fixed scroll 1 and the inner peripheral surface 13A of the wrap portion 13 of the orbiting scroll 11 and the space S2 between the proximate portion 14 of the wrap portion 13 of the orbiting scroll 11 and the inner peripheral surface 3A of the wrap portion 3 of the fixed scroll 1 are governed by the relationship S1<S2, as shown in Eq. 1. Therefore, when the wrap portions 3 and 13 make contact with each other, the proximate portion 8 of the outer peripheral surface 3B of the wrap portion 3 of the fixed scroll 1 can be first brought into contact with the inner peripheral surface 13A of the wrap portion 13 of the orbiting scroll 11. Therefore, the orbiting scroll 11 can be rotated in the same direction as that of a rotating force, with the contact portions serving as fulcrums. Thus, it is possible to eliminate backlash in the rotation-preventing mechanism (not shown), etc. and hence it is also possible to improve a compression performance.

In the first embodiment, flat surfaces 8A and 14A are used to connect adjacent proximate portions 8 and 14. However, the present invention is not limited to this but can be arranged, as illustrated, for example, in FIG. 7 showing a first example of modification in which convex surfaces 8A′ and 14A′ are used to connect the adjacent proximate portions 8 and 14. In this case, the convex surfaces 8A′ and 14A′ are formed to have a curvature smaller than that of the wrap portion 3 and 13, so as to prevent the convex surfaces 8A′ and 14A′ from making contact with the inner peripheral surfaces 13A and 3A of the mating wrap portions 13 and 3 before the proximate portions 8 and 14.

In the first embodiment, the wrap portion 3 of the fixed scroll 1 and the wrap portion 13 of the orbiting scroll 11 are both provided with proximate portions 8 and 14. Alternatively, proximate portions can be formed only on either the fixed scroll or the orbiting scroll.

Further, the proximate portions 8 and 14 can be each provided, on a tip thereof, for example, with a flat surface having a small width (for example, a few μm) in the winding direction.

In the first embodiment, from the radially inner side to the radially outer side of the wrap portions 3 and 13, the adjacent proximate portions 8, 14 are spaced apart by the constant angle α. However, the present invention is not limited to this, but the angular spacing between adjacent proximate portions on the radially inner side of the wrap portion can be different from that on the radially outer side of the wrap portion.

Next, FIGS. 8 and 9 shows the second embodiment of the present invention. This embodiment is characterized in that a plurality of flat proximate surfaces are formed on an inner peripheral surface of a wrap portion of each scroll, such that the proximate surfaces are spaced apart in the winding direction. In this embodiment, components described in the first embodiment are denoted by the same reference numerals, and descriptions thereof are omitted.

Reference numeral 21 denotes a fixed scroll of a scroll air compressor. Substantially similar to the first embodiment, the fixed scroll 21 comprises an end plate 22, a wrap portion 23, a cylindrical portion 24, a flange portion (not shown), and others. The wrap portion 23 is spirally formed and has an inner peripheral surface 23A and an outer peripheral surface 23B.

Reference numeral 25 denotes a plurality of proximate portions formed on the outer peripheral surface 23B of the wrap portion 23. Substantially similar to the proximate portions 8 of the first embodiment, the proximate portions 25 are spaced apart by the angle α in the winding direction (direction of length) of the wrap portion 23 and extend in the axial direction. Flat surfaces 25A are used to connect adjacent proximate portions 25, such that the outer peripheral surface 23B of the wrap portion 23 has a polyangular shape in transverse cross section. The proximate portions 25 are adapted to make contact with or come closest to an inner peripheral surface 28A of a wrap portion 28 of a mating orbiting scroll 27.

Reference numeral 26 denotes a plurality of flat proximate surfaces formed on the inner peripheral surface 23A of the wrap portion 23. The proximate surfaces 26 are spaced apart, for example, by the same angle α as that of the proximate portions 29 in the winding direction (direction of length). Adjacent proximate surfaces 26 are connected by recesses 26A depressed in a (radially outward) direction away from the wrap portion 28 of the orbiting scroll 27, such that the inner peripheral surface 23A of the wrap portion 23 has a polyangular shape in transverse cross section. Adjacent recesses 26A are displaced by half a phase relative to the mating proximate portions 29. In this way, the middle portion of each proximate surface 26 in the winding direction makes contact with or comes closest to the respective proximate portion 29 of the outer peripheral surface 28B of the mating wrap portion 28. The recesses 26A are formed, by a tool such as an end mill, into a curved surface having a radius substantially the same as that of the tool.

Reference numeral 27 denotes an orbiting scroll disposed to face the fixed scroll 21. Substantially similar to the first embodiment, the orbiting scroll 27 comprises a spiral wrap portion 28 formed on an end plate (not shown), the wrap portion 28 having an inner peripheral surface 28A and an outer peripheral surface 28B.

Reference numeral 29 denotes a plurality of proximate portions formed on the outer peripheral surface 28B of the wrap portion 28. Substantially similar to the proximate portions 14 of the first embodiment, the proximate portions 29 are spaced apart by the angle α in the winding direction (direction of length) of the wrap portion 28 and extend in the axial direction. Adjacent proximate portions 29 are connected by flat surfaces 29A.

Reference numeral 30 denotes a plurality of flat proximate surfaces formed on the inner peripheral surface 28A of the wrap portion 28. The proximate surfaces 30 are spaced apart, for example, by the same angle α as that of the proximate portions 25 in the winding direction (direction of length). Adjacent proximate surfaces 30 are connected by recesses 30A depressed in a direction away from the wrap portion 23 of the fixed scroll 21. Adjacent recesses 30A are displaced by half a phase relative to the mating proximate portions 25.

In this way, the inner and outer peripheral surfaces 28A and 28B of the wrap portion 28 have a polyangular shape in transverse cross section. The proximate portions 29 are adapted to make contact with or come closest to the proximate surfaces 26, and the proximate surfaces 30 are adapted to make contact with or come closest to the proximate portions 25.

This embodiment structured as described above can also bring about effects substantially the same as those of the first embodiment. Particularly in this embodiment, a plurality of flat proximate surfaces 26 and 30 are formed on the inner peripheral surfaces 23A and 28A of the wrap portions 23 and 28 and spaced apart in the winding direction. Therefore, compared to a case in which the inner peripheral surfaces 23A and 28A are curved along involute curves, the proximate portions 25 and 29 and the proximate surfaces 30 and 26 make surface contact, closer to line contact, with each other. In other words, even when the angle α between adjacent proximate portions 25 and 29 is set to be the same value as that of the first embodiment, a galling resistance can be further improved, as compared to the first embodiment.

With the plurality of flat proximate surfaces 26 and 30 formed on the inner peripheral surfaces 23A and 28A of the wrap portions 23 and 28 and spaced apart in the winding direction, the transverse cross sections of the inner peripheral surfaces 23A and 28A, as well as the outer peripheral surfaces 23B and 28B of the wrap portions 23 and 28 of the scroll 21 and 27, can be formed in a polyangular shape. Therefore, the shapes of the wrap portions 23 and 28 can be simplified. As a result, the amount of time required to form the wrap portions 23 and 28 can be further reduced, and productivity can be improved.

In the second embodiment, the proximate surfaces 26 and 30 are flat planes. However, the present invention is not limited to this, but instead, proximate surfaces 26″ and 30″ can be formed, for example, in a recessed curve (concave surface), as indicated by single-dashed lines in FIG. 10. In this case, the curvature of the proximate surfaces 26″ and 30″ is set to a value smaller than that of involute curves of the wrap portions 23 and 28, such that only middle portions of the proximate surfaces 26′ and 30′ make contact with the outer peripheral surfaces 28B and 23B of the mating wrap portions 28 and 23. In this way, compared to a case in which proximate surfaces 26 and 30 are formed in flat planes, galling resistance decreases, but the gap between the wrap portions 23 and 28 can be reduced with a result of improved compression performance.

Alternatively, proximate surfaces 26′ and 30′ can be formed in a projecting curve (convex surface), as indicated by double-dashed lines in FIG. 10. In this case, compared to the case in which the proximate surfaces 26 and 30 are formed in flat planes, compression performance decreases, but galling resistance increases.

In the second embodiment, the wrap portion 3 of the fixed scroll 1 and the wrap portion 13 of the orbiting scroll 11 are provided with proximate surfaces 26 and 30. However, instead, proximate surfaces can be formed only on either the fixed scroll or the orbiting scroll.

Next, FIG. 11 shows the third embodiment of the present invention. This embodiment is characterized in that a soft coating is applied to an outer peripheral surface of a wrap portion of each scroll. In this embodiment, components described in the first embodiment are denoted by the same reference numerals, and the descriptions thereof are omitted.

Reference numeral 31 denotes the soft coating applied to the outer peripheral surface 3B of the wrap portion 3 of the fixed scroll 1. The soft coating 31 is made of a resin material (for example, a fluorine-based resin) or a non-resin material (for example, graphite, molybdenum disulfide, boron nitride) that is smooth and heat resistant, and has a thickness of, for example, about 60 μm. The soft coating 31 is applied to and cured on the wrap portion 3, for example, by dipping or using a coating means such as a spray. In this way, the proximate portions 8 and flat surfaces 8A formed on the outer peripheral surface 3B of the wrap portion 3 are covered with the soft coating 31.

Reference numeral 32 denotes a soft coating applied to the outer peripheral surface 13B of the wrap portion 13 of the orbiting scroll 11. Substantially similar to the soft coating 31, the soft coating 32 is made of, for example, a fluorine-based resin material or a non-resin material based on molybdenum or the like and is applied to and cured in a thickness of, for example, 60 μm on the wrap portion 13, using a coating means such as a spray. In this way, the proximate portions 14 and flat surfaces 14A formed on the outer peripheral surface 13B of the wrap portion 13 are covered with the soft coating 32.

The soft coatings 31 and 32 prevent the proximate portions 8 and 14 from making direct contact with the mating wrap portions 13 and 3, even in a case that the proximate portions 8 and 14 are too close to the mating wrap portions 13 and 3 due to, for example, dimension errors, assembly errors, and the like of the scrolls 1 and 11 and the proximate portions 8 and 14.

The soft coatings 31 and 32 are sized in thickness to allow only the proximate portions 8 and 14 positioned at apexes of a polygon to make contact. By setting a gap between the proximate portions 8 and 14 and the inner peripheral surfaces 13A and 3A of the wrap portions 13 and 3 to zero or below, compression efficiency can be improved by about 10 percent in the overall adiabatic efficiency. A result of an experiment shows that with the gap set to 40 μm, the overall adiabatic efficiency is 50 percent, whereas with the gap set to 0 μm, the overall adiabatic efficiency increases to 60 percent.

Even when such contact occurs, the soft coatings 31 and 32 can be readily compressed under contact with the mating wrap portions 13 and 3, or deformed by being worn off, so as to conform to a range of movement of the proximate portions 8 and 14.

Therefore, this embodiment structured as described above can also bring about effects substantially the same as those of the first embodiment. Particularly in this embodiment, the soft coatings 31 and 32 are applied to the outer peripheral surfaces 3B and 13B of the wrap portions 3 and 13. Therefore, in a case in which the proximate portions 8 and 14 are too close to the mating wrap portions 13 and 3 due to dimension errors, assembly errors, and the like of a machine, for example, the soft coatings 31 and 32 make contact with the inner peripheral surfaces 13A and 3A of the mating wrap portions 13 and 3. In this case, the soft coatings 31 and 32 can be readily deformed and caused to fit with the mating wrap portions 13 and 3 by making contact with them, so as to prevent galling therebetween, damage or the like, a loss in power, any increase in noise, or the like.

The maximum gap between the wrap portions 3 and 13 can be also reduced by increasing the angle α between adjacent proximate portions 8 and 14. Therefore, even when galling resistance is increased by setting the angle α to, for example, about 7.5 degrees (α=0.13 (rad)), the compression performance can remain high. As a result, both the galling resistance and compression performance can be improved.

The soft coatings 31 and 32 are subject, only at portions thereof pinched between the proximate portions 8 and 14 and the wrap portion, to deformation. The size of the gap formed between the wrap portions 3 and 13 of the scrolls 1 and 11 can be made smaller at the trapping position of the compression chamber 15. Therefore, the degree of hermeticity and compression efficiency of the compression chamber 15 can be improved. Further, even in the case that the range of movement of the proximate portions 8 and 14 varies, for example, due to dimension errors, assembly errors, and the like of a machine, variations in the range of movement of the proximate portions 8 and 14 can be compensated by the soft materials 31 and 32. Therefore, the scrolls 1 and 11 can be machined, assembled, and so on with minimum precision. As a result, compressors can be produced efficiently.

In the third embodiment, the soft coatings 31 and 32 are applied only to the outer peripheral surfaces 3B and 13B of the wrap portions 3 and 13. However, the present invention is not limited to this, but instead, soft coatings can be applied, for example, only to the inner peripheral surfaces 3A and 13A of the wrap portions 3 and 13. Alternatively, soft coatings can be applied to both the inner and outer peripheral surfaces 3A and 3B of the wrap portion 3, to both the inner and outer peripheral surfaces 13A and 13B of the wrap portion 13, or to all of the inner and outer peripheral surfaces 3A, 13A, 3B, and 13B of the wrap portions 3 and 13.

In the third embodiment, the soft coatings 31 and 32 are applied to the wrap portions 3 and 13 of the scrolls 1 and 11 similar to those of the first embodiment. However, instead, soft coatings can be applied to wrap portions of scrolls similar to, for example, those of the second embodiment.

Next, FIGS. 12 to 14 show the fourth embodiment of the present invention. This embodiment is characterized in that proximate portions of a wrap portion are formed only on a part away from an end plate in the axial direction. In this embodiment, components described in the first embodiment are denoted by the same reference numerals, and the descriptions thereof are omitted.

Reference numeral 41 denotes a fixed scroll of a scroll air compressor. As shown in FIG. 12, the fixed scroll 41, which is substantially the same as that of the first embodiment, comprises an end plate 42 of a substantially disk shape, a spiral wrap portion 43 projecting in the axial direction from a surface of the end plate 42, a flange portion (not shown), and others.

An inner peripheral surface 43 a of the wrap portion 43 is smoothly curved without recesses or projections, and an outer peripheral surface 43B of the wrap portion 43 is provided with proximate portions 51 (described later). As shown in FIGS. 13 and 14, a groove 43C having a U shape in cross section is formed in an edge of the wrap portion 43. The groove 43 c is provided with a spiral tip seal 44. The tip seal 44 is adapted to elastically slidingly contact with a surface of an end plate 48 of an orbiting scroll 47 (described later), so as to prevent compressed air from leaking out.

Reference numeral 45 denotes a plurality of proximate portions formed on the outer peripheral surface 43B of the wrap portion 43 of the fixed scroll 41. Substantially similar to the proximate portions 8 of the first embodiment, the proximate portions 45 are spaced apart in the winding direction of the wrap portion 43 and extend in the axial direction. It is to be noted that the meaning of extending in the axial direction is not limited to extending parallel (the angle of inclination 0°) to the axial direction, but includes extending, for example, in a direction inclined ±10° to 20° relative to the axial direction.

The proximate portion 45 extends in the axial direction from an edge to an intermediate position of the wrap portion 43 toward a root of the wrap portion 43. In other words, the proximate portion 45 is formed only on the edge side of the wrap portion 43 away from the end plate 42 in the axial direction. Adjacent proximate portions 45 on the edge side of the wrap portion 43 are connected by flat surfaces 45A. A portion on the root side of the outer peripheral surface 43B of the wrap portion 43 (on the outer peripheral surface 43B except the proximate portions 45 and flat surfaces 45A) is formed into a smoothly curved surface without recesses or projections. Further, the portion on the root side of the outer peripheral surface 43B of the wrap portion 43 extends continuously with the proximate portions 45, so as to form a single surface.

Reference numeral 46 denotes a stepped portion formed on the root side of the wrap portion 43 of the fixed scroll 41. The stepped portion 46 is formed wider than the portion on the edge side of the wrap portion 43 and projects towards the outer peripheral surface 49B of the wrap portion 49 of the orbiting scroll 47, which mates with the inner peripheral surface 43A. The stepped portion 46 extends approximately the same length as proximate portions 51 of a wrap portion 49 (described later) in the axial direction, so as to face the proximate portions 51.

Reference numeral 47 denotes an orbiting scroll that is disposed to face the fixed scroll 41. As shown in FIGS. 12 and 14, the orbiting scroll 47, which is substantially similar to that of the first embodiment, mainly comprises an end plate 48 of a disk shape and a spiral wrap portion 49 projecting in the axial direction from a surface of the end plate 48.

The wrap portion 49 has: an inner peripheral surface 49A that is smoothly curved without recesses or projections; and an outer peripheral surface 49B that is provided with proximate portions 51 (described later). Further, the wrap portion 49 is provided, on an edge thereof, with a groove 49C having a U shape in cross section, the groove 49C having a tip seal 50 attached thereto.

Reference numeral 51 denotes a plurality of proximate portions formed on the outer peripheral surface 49B of the wrap portion 49 of the orbiting scroll 47. Substantially similar to the proximate portions 14 of the first embodiment, the proximate portions 51 are spaced apart in the winding direction of the wrap portion 49 and extend in the axial direction.

Substantially similar to the proximate portions 45, the proximate portions 51 extend in the axial direction from an edge to an intermediate portion of the wrap portion 49 toward a root of the wrap portion 49, such that the proximate portions 51 are formed only on the edge side of the wrap portion 49 in the axial direction away from the end plate 48. On the other hand, adjacent proximate portions 51 on the edge side of the wrap portion 49 are connected by flat surfaces 51A. A portion of the outer peripheral surface 49B of the wrap portion 49 on the root side (a portion except the proximate portions 51 and flat surfaces 51A) is formed into a smoothly curved surface without recesses or projections. Further, a portion of the outer peripheral surface 49B of the wrap portion 49 on the root side extends continuously with the proximate portions 51, so as to form a single surface.

Reference numeral 52 denotes a stepped portion formed on the root side of the wrap portion 49 of the orbiting scroll 47. Substantially similar to the stepped portion 46 of the wrap portion 43, the stepped portion 52 is formed wider than the portion on the edge side of the wrap portion 49 and projects toward the outer peripheral surface 43B of the wrap portion 43 of the fixed scroll 41, which mates with the inner peripheral surface 49A. The stepped portion 52 extends substantially the same length in the axial direction as the proximate portions 45 of the wrap portion 49, so as to face the proximate portions 45.

Therefore, this embodiment structured as described above can also bring about substantial the same effects as those of the first embodiment. Particularly in this embodiment, the proximate portions 45 and 51 are formed only on parts of the wrap portions 43 and 49 away from the end plates 42 and 48 in the axial direction. As a result, the axial dimensions of the proximate portions 45 and 51 can be decreased, and abnormal noise generated by the proximate portions 45 and 51 can be reduced.

Since the dimensions of the proximate portions 45 and 51 can be reduced in the axial direction of the wrap portions 43 and 49, an average radial gap between the wrap portion 43 of the fixed scroll 41 and the wrap portion 49 of the orbiting scroll 47 can be reduced with a result of improved compression efficiency. Further, the improved compression efficiency can reduce the temperature within the wrap portions 43 and 49. As a result, the life time of the tip seals 44, 50, and so on can be extended.

Particularly in this embodiment, the proximate portions 45 and 51 can be formed only on the edge portions of the wrap portions 43 and 49, where thermal deformation occurs markedly. As a result, galling due to thermal deformation can be prevented, while the proximate portions 45 and 51 can be brought closest to or into contact with the mating wrap portions 49 and 43, so as to further improve the compression efficiency.

The proximate portions 45 and 51 are not formed on the root sides of the wrap portions 43 and 49, and the outer peripheral surfaces 43B and 49B of the wrap portions 43 and 49 on the root sides are formed on the same curved surface as the proximate portions 45 and 51. Therefore, dimension control on the root side can be readily conducted.

In the fourth embodiment, the scrolls 41 and 47, which have proximate portions 45 and 51 on the outer peripheral surfaces 43B and 49B of the wrap portions 43 and 49 as in the first embodiment, are provided with proximate portions 45 and 51 that are formed only on the edge sides of the wrap portions 43 and 49. However, the present invention is not limited to this, but instead, scrolls similar to those of the second or third embodiment, for example, can be provided with proximate portions on only edge sides of wrap portions.

Next, FIG. 15 shows the fifth embodiment of the present invention. This embodiment is characterized in that an involute curved surface is formed along an involute curve on a radially outer side of a wrap portion. In this embodiment, components described in the first embodiment are denoted by the same reference numerals, and descriptions thereof are omitted.

Reference numeral 61 denotes a fixed scroll of a scroll air compressor. Substantially similar to that of the first embodiment, the fixed scroll 61 comprises an end plate 62, a wrap portion 63, a cylindrical portion 64, a flange portion (not shown), and others. The wrap portion 63 is spirally formed and has an inner peripheral surface 63A and an outer peripheral surface 63B.

However, a plurality of proximate portions 65 and flat surfaces 65A are formed over the entire axial length of the outer peripheral surface 63B of the wrap portion 63. The wrap portion 63 is not provided on the radially outer side (on the spiral terminating end) with the proximate portions 65, but with an involute curved surface 63C along an involute curve. The involute curved surface 63C extends, for example, along a length equivalent to approximately one turn radially inward from the radially outer end of the wrap portion 63 and is disposed at a position that serves as a peripheral wall of compression chambers 15′ and 15″ on the radially outer side of the wrap portion 63.

Reference numeral 66 denotes an orbiting scroll disposed to face the fixed scroll 61. Substantially similar to that of the first embodiment, the orbiting scroll 66 comprises a spiral wrap portion 67 projecting from an end plate (not shown). The wrap portion 67 has an inner peripheral surface 67A and an outer peripheral surface 67B.

The outer peripheral surface 67B of the wrap portion 67 is provided, over the entire axial length thereof, with proximate portions 68 and flat surfaces 68A. Substantially similar to the wrap portion 63 of the fixed scroll 61, the wrap portion 67 is provided, on the radially outer side (on the spiral terminating end), not with the proximate portions 68, but with an involute curved surface 67C along an involute curve. The involute curved surface 67C extends, for example, along a length equivalent to about one and half turn radially inward from an end of the radially outward side of the wrap portion 67 and is disposed at a position that serves as a peripheral wall of compression chambers 15′ and 15″ on the radially outer side of the wrap portion 67.

In this embodiment, the involute curved surfaces 63C and 67C are formed at positions facing the compression chambers 15′ and 15″ on the radially outer side of the wrap portions 63 and 67. Therefore, when the compressor is in operation, smooth, continuous sliding contact between the wrap portion 63 of the fixed scroll 61 and the wrap portion 67 of the orbiting scroll 66 can be made at the position of the compression chambers 15′ and 15″ on the radially outer side.

As a result, this embodiment structured as described above can also bring about substantially the same effects as those of the first embodiment. Particularly in this embodiment, the involute curved surface 63C is formed in a part of the wrap portion 63 of the fixed scroll 61 equivalent to about one turn on the radially outer side. Further, the involute curved surface 67C is formed on a part of the wrap portion 67 of the orbiting scroll 66 equivalent to about one and half turns on the radially outer side. In this way, desirable sealing closure of the compression chamber 15′ and its adjacent compression chamber 15″ can be maintained at a compression starting position S.

Therefore, stable air compression can be performed in the compression chambers 15′ and 15″ on the radially outer side that greatly influence a volumetric efficiency during the compression, so as to improve compression efficiency. Abnormal noise generated by the proximate portions 65 and 68 on the radially inner side can be prevented from leaking through the suction opening 6, thereby reducing noise.

In the fifth embodiment, the involute curved portions 63C and 67C are formed on the scroll 61 and 66 having proximate portions 65 and 68 on the outer peripheral surfaces 63B and 67B of the wrap portions 63 and 67, as in the first embodiment. However, the present invention is not limited to this, but involute curved surfaces can be provided, for example, on wrap portions of scrolls similar to those of the second to fourth embodiments.

The above embodiments are described in terms of a scroll air compressor as an example, in which the orbiting scrolls 11, 27, 47, and 66 are orbited relative to the fixed scroll 1, 21, 41, and 61 fixed to casings. However, the present invention is not limited to this, but can be applied to a full-rotating type scroll fluid machine, for example, in which two scrolls disposed facing each other are driven to rotate, respectively, as disclosed in Japanese Patent Application Unexamined Publication (KOKAI) No. Hei 9-133087.

Further, the above embodiments are described in terms of an example in which a scroll air compressor is used as a scroll fluid machine. However, the present application is not limited to this, but can be applied to other scroll fluid machines, e.g. a refrigerant compressor for compressing a refrigerant.

As described above, according to the above embodiment, adjacent proximate portions are connected by flat surfaces or convex surfaces. Therefore, there is no recess between adjacent projections, as in the prior art. A gap between opposing wrap portions can be narrowed to reduce an amount of fluid filled between the wrap portions with a result of improved compression efficiency.

Further, the adjacent proximate portions are connected by flat surfaces or convex surfaces, such that the outer peripheral surface of the wrap portion having the proximate portions can be formed in a polyangular shape in transverse cross section. In this way, the shape of the wrap portion can be simplified, compared to a case in which projections are formed on a curved peripheral surface of a wrap portion, as in the prior art. As a result, when a wrap portion is formed using a tool such as an end mill, the end mill does not need to be moved back and forth in the radial direction, and the number of times the direction of movement of the tool has to be changed can be reduced. Therefore, the present invention is less susceptible to an influence of backlash of a processing machine in a reciprocating movement. Therefore, machining errors can be reduced, and wrap portions can be produced consistently with high precision. Compared to a conventional one having projections, a distance of movement of a processing machine can be reduced, and the number of changes in machining direction can be reduced. Therefore, an amount of time required to form a wrap portion can be reduced with a result of improved productivity. Further, a machining program can be readily made by providing coordinates of apexes of a polyangular shape, and the coordinates of the apexes can be readily changed. Therefore, the shape of the wrap portion can be readily changed, for example, according to specifications of a machine.

The proximate portions can be readily blunted or worn off when making contact with a peripheral surface of an opposing wrap portion, and thus can fit with the peripheral surface of the wrap portion, before making contact with it a large number of times. This makes it possible to reduce power loss and to prevent damage, noise, galling, and so on, and moreover to enhance durability and reliability.

Further, as the angle between adjacent proximate portions of the wrap portions increases, a galling resistance increases, but a compression performance decreases. On the other hand, as the angle between the adjacent proximate portions of the wrap portions decreases, the galling resistance decreases, but the compression performance increases. Therefore, machines with desired properties can be produced by providing an optimum balance between these opposing properties.

According to the above embodiment, the inner peripheral surface of the wrap portion of one scroll is provided with a plurality of flat, concave, or convex proximate surfaces that are spaced apart in the winding direction and make contact with or come closest to proximate portions formed on the outer peripheral surface of the wrap portion of the other scroll. Therefore, the inner peripheral surface of the wrap portion of the one scroll can be formed in a polyangular shape in transverse cross section. In this way, the shape of the wrap portion can be simplified, the amount of time required to form the wrap portion can be further reduced, and productivity can be increased.

According to the above embodiment, a soft coating is applied to at least either the inner or outer peripheral surface of the opposing wrap portions, such that the soft coating is placed between the proximate portions and the mating wrap portion. Therefore, when the proximate portions come too close to the mating wrap portion due to, for example, errors in machine dimension, assembly, or the like, the soft coating makes contact with the proximate portions or the mating wrap portion. In this case, the soft coating can be readily deformed by the contact with the proximate portions or the mating wrap portion and fit with the proximate portions or the mating wrap portion, so as to prevent galling, damage, and so on therebetween and an increase in power loss, noise, and so on.

The soft coating is subject, only at a portion thereof that is pinched between the proximate portions and the wrap portion, to deformation. The size of the gap formed between the wrap portions of the scrolls can be made smaller at the trapping position of the compression chamber. As a result, a degree of hermeticity and compression efficiency of the compression chamber can be improved. Further, in a case that the range of movement of the proximate portions varies due to, for example, errors in machine dimension, assembly, and the like, these variations in the range of movement of the proximate portions can be compensated for by the soft coating. Therefore, scrolls can be machined, assembled, and so on with minimum precision. This makes it possible to produce scroll fluid machines efficiently.

According to the above embodiment, the pitch P of the proximate portion in the winding direction is narrow on the radially inner side and is wide on the radially outer side. Therefore, as the radius of curvature of the wrap portion becomes smaller on the radially inner side, a plurality of proximate portions can be narrowly spaced apart along the radius of curvature. As a result, the gap between the opposing wrap portions in the radial direction can be made small to increase the degree of hermeticity of the compression chambers and thus improve the compression performance.

According to the above embodiment, the proximate portions are formed at angular spacings that are substantially constant over the range between the radially inner side and the radially outer side of the wrap portion. Therefore, the dimensions of the pitches of the proximate portions in the winding direction can be made small on the radially inner side and wide on the radially outer side. In this case, the radius of curvature of the wrap portion is small on the radially inner side, but a plurality of proximate portions can be formed with a narrow pitch along the radius of curvature. The degree of hermeticity of the compression chambers can be enhanced by reducing the gap between the opposing wrap portions in the radial direction. As a result, the compression performance can be improved.

According to the above embodiment, the proximate portions formed only in a part of the wrap portion away from the end plate in the axial direction. Therefore, during an orbiting motion of one scroll, for example, the proximate portions of the scroll can be brought closest to or into contact with the wrap portion of another scroll at the trapping position of each compression chamber. As a result, the degree of hermeticity of the compression chambers can be increased by the proximate portions.

Since the proximate portions are formed only on a part of the wrap portion away from the end plate in the axial direction, the axial dimension of the proximate portions can be reduced, and abnormal noise generated by the proximate portions can be reduced. Further, since the proximate portions can be reduced relative to the axial dimension of the wrap portion, the average gap between the wrap portions of the fixed scroll and the orbiting scroll can be reduced with a result of improved compression efficiency. Further, the temperature in the wrap portions can be lowered, and thus the life time of the tip seals and so on becomes longer. In the case that proximate portions are formed at edges of the wrap portions where thermal deformation occurs markedly, galling due to thermal deformation can be prevented by the proximate portions.

Further, on the root side of the wrap portions, the gap between the outer peripheral surface of the wrap portion and the inner peripheral surface of the mating wrap portion can be set to substantially the same dimension as that without the proximate portions. Therefore, contact between the wrap portions can be prevented at this position, and reliability can be enhanced.

Further, according to the above embodiment, the proximate portions are formed only on a part of the wrap portions on the radially inner side in the winding direction. Further, the wrap portions are provided, on the radially outer side thereof, with involute curved surfaces. Therefore, for example, at the trapping position and so on of the compression chamber defined on the radially outermost side of the wrap portions, smooth peripheral surfaces of the wrap portions can be brought closest to or into contact with each other. As a result, the compression chamber on the radially outer side, which greatly influences the volumetric efficiency during compression, can be sealed desirably with a result of improved compression performance.

Particularly, since a temperature rise due to compression heat is small on the outer peripheral side of the wrap portions, galling is less likely to occur. Therefore, on the involute curved surface formed on the outer peripheral side of a wrap portion, the dimension of the gap between the wrap portion and another wrap portion can be reduced. This makes it possible to reliably bring the smooth peripheral surfaces closest to or into contact with each other on the radially outer side of the wrap portions, thereby preventing any abnormal noise generated by the proximate portions on the radially inner side of the wrap portions, from leaking to the outside through a suction opening and so on provided on the radially outer side.

Although only some exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teaching and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention.

The present application claims priority under 35 U.S.C. section 119 to Japanese Patent Application No. 2006-354444, filed on Dec. 28, 2006. The entire disclosure of Japanese Patent Applications No. 2006-354444 including specification, claims, drawings and summary is incorporated herein by reference in its entirety. 

1. A scroll fluid machine comprising: a first scroll having a wrap portion projecting axially from an end plate, said wrap portion being wound spirally from a radially inner side toward a radially outer side of said end plate; and a second scroll provided facing said first scroll, said second scroll having a wrap portion projecting axially from an end plate, said wrap portion being wound spirally from a radially inner side toward a radially outer side of said end plate so as to overlap the wrap portion of said first scroll to define a plurality of compression chambers; wherein a plurality of proximate portions are formed at least on an outer peripheral surface of the wrap portion of the first scroll, the plurality of proximate portions being adapted to make contact with or come closest to an inner peripheral surface of the wrap portion of the second scroll and being spaced apart in a winding direction; the adjacent proximate portions are connected by flat surfaces or convex surfaces; and the flat surfaces or convex surfaces are positioned farther than the proximate portions away from the second scroll.
 2. A scroll fluid machine according to claim 1, wherein a plurality of flat, concave, or convex proximate surfaces are formed on an inner peripheral surface of the wrap portion of the second scroll, the plurality of flat, concave, or convex proximate surfaces being adapted to make contact with or come closest to the proximate portions formed on the outer peripheral surface of the wrap portion of the first scroll and being spaced apart in the winding direction.
 3. A scroll fluid machine according to claim 1, wherein a film-like soft coating, which is made of a material softer than that of the proximate portions, is applied to at least either the outer peripheral surface of the wrap portion of the first scroll or the inner peripheral surface of the wrap portion of the second scroll.
 4. A scroll fluid machine according to claim 1, wherein the proximate portions are formed such that a pitch thereof in the winding direction is narrow on the radially inner side and wide on the radially outer side.
 5. A scroll fluid machine according to claim 1, wherein the proximate portions are formed at equal angular spacings throughout the wrap portion from the radially inner side to the radially outer side.
 6. A scroll fluid machine according to claim 1, wherein the proximate portions are formed only on a part of the wrap portion away from the end plate in the axial direction, the wrap portion projecting from the end plate.
 7. A scroll fluid machine according to claim 1, wherein the proximate portions are formed only on the radially inner side of the wrap portion in the winding direction, and an involute curved surface is formed along an involute curve on the radially outer side of the wrap portion. 